The present invention generally relates to packaging and more particularly is directed to an apparatus for making unitary packages wrapped on all sides which hold a plurality of components, each package containing a load wrapped and enclosed by stretched film.
Case packing or boxing is a common way of shipping multiple unit products so that the products are encased on all sides. Multiple unit products are generally stacked in a corrugated box or are wrapped with draft paper with the ends of the draft paper being glued or taped.
Customer dissatisfaction with gluing is high because removal of glued cartons or bags from the unitized loads tends to tear the outside layers of the cartons. Glue, although an inexpensive material, demands interleaving for product orientation requiring more durable and expensive packaging material.
Alternatively, tape is used to horizontally bind the top layer of the load. However, tape is expensive and allows relatively free movement of all product surrounded.
Another way of packaging contained products is by putting a sleeve or covering of heat shrinkable material around the load, placing a bottom and top cover on the load and shrinking the sleeve and covers to form a unitized enclosed package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798; 3,626,654; 3,590,549; and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
Yet another way of packaging contained products is by placing a top and bottom cover sheet on the product load and wrapping the products with a web of stretched plastic film to unitize the load. Thus, four sides of the load are placed under a containment force while the ends are not under a containment force.
The elasticity of stretched plastic film holds the product of the load under more tension than either shrink wrap of kraft wrap, particularly with products which settle when packaged. The effectiveness of stretched plastic film in holding a load together is a function of the containment or stretch force being placed on the load and the ultimate strength of the total layered film wrap. These two functions are determined by the modulus or hardness of the film after stretch has occurred and the ultimate strength of the film after application.
The use of wrapping machinery to wrap stretched film around a load is well known is the art. Four types of stretch wrapping apparatus are commonly used in the packaging industry and these types are generally described as spiral rotary machines, full web rotary machines, pass through machines, and circular rotating machines. These machines have typically used top and bottom covers to provide for complete enclosure of the load.
Several load enclosure apparatuses are known which employ a spiral wrap. U.S. Pat. No. 603,585 discloses a spiral wrapping device for enclosing individual newspapers in paper wrap for mailing purposes. Each newspaper is placed on a cylindrical core with a circumference approximately twice that of a newspaper, and each newspaper advances along the length of the core as the core is rotated. Wrapping paper is applied to the core at an angle and the wrapping between newspapers is severed as each newspaper reaches the end of the cylinder and is placed on a flat horizontal surface, thereby collapsing the wrapping paper against the underside of the newspaper previously pressed to the cylinder.
U.S. Pat. No. 1,417,591 discloses a wrapping machine for individual items such as boxes in which each such item is conveyed along the surface of a horizontal sheet of wrapping material. The edges of wrapping material on each side of an item are curled upward to meet one another atop the item to be wrapped thereby forming a tube around the item. The leading end of the tube is sealed and the trailing end of the tube is severed and then sealed to enclose the item. Another device which utilizes this system of wrapping is disclosed in U.S. Pat. No. 3,473,288.
In U.S. Pat. No. 2,575,467, a wrapper of cylindrical packages for material such as sausage is disclosed in which the package is rotated about its cylindrical axis as wrapping tape is applied at an angle to form a cylindrical wrap. A rotating wheel forms the stuffed casing into twisted links.
In U.S. Pat. No. 2,863,270, two cylindrical items of approximately equal diameter are abutted at their planar ends, and placed by hand in a cradle which exposes the complete circumference of the abutting ends. A roll of wrapping material is then driven by a hand crank mechanism to circulate around the circumference of the abutting end, applying wrapping material thereto. When sealed together, the pair of cylindrical items are removed from the cradle by hand.
A spiral wrapping machine for long bundles of items such as filaments is disclosed in U.S. Pat. No. 3,000,167. As the bundle of filaments moves along its axis through the wrapping area, a ring circulates about the bundle carrying a roll of wrapping material which is applied to the bundle to form a spiral wrap pattern.
A full web rotary machine which can use a top and bottom sheet to form an enclosed packaged load is shown by U.S. Pat. No. 3,867,806.
A typical disclosure of a load enclosure in pass through wrapping is found in U.S. Pat. No. 3,640,048 which shows that film may be applied to the top and bottom of the pallet load prior to the wrapping cycle when it is desired to cover all six surfaces of the pallet load with film.
A load enclosure performed with a circular rotating machine is typified by U.S. Pat. No. 4,050,220. This patent discloses a wrapping device for multiple unit loads. Each load is conveyed to a wrapping area in which a load is supported on one or more stationary planar surfaces. The leading edge of a roll of stretchable plastic wrapping material is held adjacent to the load, and the roll of material is rotated about the load and the supporting planar surfaces, wrapping the load and supporting surfaces together. Plastic wrapping material is stretched during the wrapping operation so that the material is under tension when applied to the load. After the wrapping cycle is complete, the load is pushed past the ends of the supporting surfaces, and the wrapping material which covered the supporting surfaces collapses against the sides of the load. Further developments of circular rotary wrapping apparatus are disclosed in U.S. Pat. Nos. 4,110,957 and 4,178,734.
Commercial circular rotating wrapping machines are presently manufactured by Lantech, Inc., under the trademark LANRINGER and are provided with wrapping ring inner diameters of 36 inches, 54 inches, 72 inches, and 84 inches. In differentiating between the various circular rotating wrapping machines manufactured by Lantech, Inc., the manual model has the designation SR; the full web models have the designation SVR and SAVR; the spiral models have the designation SVSR and SAVSR, and the continuous wrap or bundler models have the model designation SVCR and SAVCR.
The present invention allows large loads to be wrapped on all sides so that a rectangular-shaped load will be wrapped on six sides with all sides being enclosed and held under a compressive force. This eliminates the need for costly top and bottom cover sheets along with the man hours or costly equipment needed to place the cover sheets on the load.
In addition, by stretching the continuous spiral wrap, the portion of the spiral wrap between the loads assumes a smaller diameter or enclosed cross-sectional area than that of the load due to the plastic film attempting to return to its original memory position. This smaller area allows the wrap to be more easily guided so that it can be sealed and severed.
The present invention overcomes problems in existing apparatus by utilizing a conveyor assembly which transports the stretched film web at the same speed as the load which is being carried through the dispensing area, thus providing a stronger wrap and eliminating disorientation, film tearing, product abrasion, and friction problems inherent in the prior art. Thus, there is not as much need to change the size of support tongues to support different weights and lengths of loads, or to make sure that there is sufficient space to hold the film from the film ring to cover the angle formed between the product and the stationary ring. As the loads are wrapped and carried into the sealing and cutting mechanism, the trailing end of each package is sealed and severed from the continuous web enclosing the load with a six sided wrap providing compression forces on each side. Simultaneously with the sealing and severing of the trailing end of the load wrap, the leading end of the following load wrap is formed.